Tetrahydrofolate dehydrogenase in blood cells and in hematopoietic organs of different vertebrate species.

Some general aspects in cytochemical demonstration of the tetrahydrofolate dehydrogenase, concerning the final reaction product, are studied. Steady and variable factors are detected in a comparative study of Vertebrate hemopoiesis: the enzyme exhibits peculiar features in different cell types. The reactivity progressively decrease in the erythropoietic series, in concomitance with hemoglobin synthesis. Conversely an increase in the intensity of reaction is found in the granulocytopoietic series; the correspondence of positive material with the specific (eosinophil and heterophil) granulations can be discussed. The thrombocytopoietic series is also labelled by this reaction.